The importance of acetylcholinesterase (AChE) lies in its physiological role in neurotransmission, it prominence as a marker for nerve-muscle interactions, and because it is a complex family of oligomeric forms with multiple subcellular locations. Studies of AChE gene expression will detail how muscle cells regulate the synthesis and assembly of synaptic components in particular, and in broader terms, will provide quantitative information concerning the mechanisms of regulation and localization of membrane and secreted proteins in electrically excitable cells. It is now clear that all AChE forms in muscle and nerves are products of a single gene and therefore the multiple synaptic forms of this protein expressed by these cells must arise either by alternative splicing or post-translational events. The goal of this proposal is to determine the molecular and cellular mechanisms regulating the biogenesis and localization of the multiple oligomeric forms of AChE in muscle. The overall objective is to determine the relative contributions of transcriptional, post-transcriptional, and post-translational events in regulating AChE localization and metabolism. The specific aims of this proposal are: 1) To obtain and characterize cDNA clones encoding the two allelic variants of AChE expressed in muscle cells as well as the multiple AChE transcripts possibly expressed in this tissue; these studies will enable us to unequivocally determine whether one or more AChE transcripts are expressed in muscle and determine the molecular basis for the assembly of the multiple oligomeric forms. 2) To associate specific cDNAs with each of the two AChE alleles as well as individual transcripts for subsequent studies on the transcriptional control of AChE synthesis and assembly by muscle activity. 3) To determine whether muscle cell nuclei behave autonomously with respect to transcription, translation, and localization of identified gene products with emphasis on the synaptic form of AChE in muscle. 4) To study the transcriptional control of AChE biogenesis and the membrane events influencing these decisions using the molecular probes currently being developed in our laboratory. And 5) To begin long range studies on the signaling mechanisms involved in regulating gene expression in electrically excitable cells using AChE as as model system.